Hertz's experiment receiver

A forum designed mainly for high school physics students in New South Wales, Australia.
r.jenkins
Posts: 11
Joined: Sat May 01, 2010 10:43 pm

Hertz's experiment receiver

Postby r.jenkins » Fri May 07, 2010 6:09 pm

Hi,
In Hertz's original experiment to verify Maxwell's prediction of electromagnetic waves, what is actually 'happening' with the receiver? What is causing it to spark also?

Thanks

User avatar
joe
Posts: 745
Joined: Fri Aug 29, 2003 11:57 am
Location: Sydney

Re: Hertz's experiment receiver

Postby joe » Sat May 08, 2010 9:22 pm

I'm afraid that I'm not a science historian so I don't know for sure: I've never read the original work.

However, from the diagrams (ring with a small gap) it would appear to be the Faraday emf generated across the gap by the varying magnetic flux through the ring.

Best
Joe

r.jenkins
Posts: 11
Joined: Sat May 01, 2010 10:43 pm

Re: Hertz's experiment receiver

Postby r.jenkins » Tue May 11, 2010 10:18 pm

Maybe I put it the wrong way!

Hertz discovered that the major factor (but not the only factor) causing the sparking was the photoelectric effect caused by the UV emission of the inducation coil and transmitting loop. When he blocked this UV there was still a small spark occuring in the receiver loop. What was still causing this small spark? Is it the natural resonance of the receiver matching radio waves being produced by the transmitting loop?

Thanks

User avatar
joe
Posts: 745
Joined: Fri Aug 29, 2003 11:57 am
Location: Sydney

Re: Hertz's experiment receiver

Postby joe » Tue May 11, 2010 11:16 pm

When he blocked this UV there was still a small spark occuring in the receiver loop. What was still causing this small spark? Is it the natural resonance of the receiver matching radio waves being produced by the transmitting loop?


I'm still not a science historian. But I assume you are talking about the Hertz receiver: a nearly complete circle of wire, with a little ball on each end, the two balls slightly separated.

In the presence of a radio wave, the magnetic flux through this circuit generates a Faraday emf that appears across the gap. Yes, the two spheres have a (small) capacitance C and the loop has a (small) inductance L, leading to a (high) resonant frequency 1/2pi*sqrt(LC).

So it's a radio receiver. As I understand it, that's why he's famous and that's why we measure frequency in Hz.

Joe


Return to “High School Physics”

Who is online

Users browsing this forum: No registered users and 1 guest